This project comprises an effort of several groups of investigators with common interest in the mechanism of ion transport. The research programs cover a broad spectrum including organ systems (kidney, intestines), isolated amphibian epithelium (bladder, colon) and single cell systems (red blood cells, bacteria). The proposed investigations seek to develop a better understanding of the properties and detailed mechanisms of active and passive transport steps in the above mentioned cell membranes. The studies also are concerned with an assessment of the metabolic dependence of transport processes, and the precise relationship between ion transport processes and electrical phenomena. Some of the projected studies deal with investigations aimed at the relationship between transport and membrane fine-structure, with pathological disturbances of membrane function and with drug effects on transport phenomena at the membrane level.